This invention relates to cooling arrangements in general and more particularly to an arrangement for cooling electrical devices having water cooled electric conductors, with deionized cooling water and a closed cooling system which contains a main loop and at least one parallel loop with a mixed bed filter.
For cooling electrical devices of high power rating, for instance generators and travelling field tubes as well as heavy duty cables, closed cooling systems are provided, as is well known. These cooling systems contain deionized cooling water, so-called deionate. The cooling water flows through the current carrying conductors of the device which generally consist of copper or copper alloys.
As is well known, secondary loops are provided for cooling particularly sensitive cooling places, for instance, the cooling heads and seals of boiler circulating and boiler feed pumps in power generating stations; these coolant loops are likewise constructed as closed cooling loops and may be provided with a mixed bed filter. In order to keep the electrolyte content in the cooling system as low as possible, a small partial stream of the cooling water which may amount to, for instance, about 0.5 to 5%, can be conducted via a parallel loop which contains the mixed bed filter. The cooling water in such a cooling system has a very low electric conductivity which can be less than 1 .mu.S/cm. Part of the copper or the copper alloy may be removed by the cooling water through corrosion and be deposited again at other points or in following parts of the system. The corrosion removal rate depends on the pH value of the cooling water and decreases with increasing pH value. The pH value has therefore been raised in secondary cooling loops in power generating stations to at least 9 (VGB-Kraftwerkstechnik 59, September 1979, pp. 720 to 724).
It is an object of the present invention to prevent deposits, especially due to corrosion, in closed cooling systems with deionized cooling water, particularly for cooling electrical devices of high power rating, having electric conductors, through which cooling water flows.